ABS resins having impact resistance and low-gloss properties and processes for preparing them

Abstract

The present invention relates to ABS (Acrylonitrile-Butadiene-Styrene) resins having excellent impact resistance, low-gloss properties and superior heat resistance, and to a process for preparing them. In particular, between 5 wt % and 20 wt % butadiene rubber having double bonds is dissolved in between 30 wt % and 70 wt % graft-copolymerizing aromatic vinyl monomer and between 10 wt % and 50 wt % cyanized vinyl monomer. Polymerization controller and radical initiator are added to the above, and the mixture polymerized in a first step of bulk polymerization at a temperature of 80°-120° C. while stirring until polymerization proceeds to between 20 and 50% of completion. Between 40% and 70% α-methyl styrene monomer, between 10 wt % and 40 wt % unsaturated nitrile and between 5 wt % and 15 wt % butadiene rubber are then added to the polymerized mixture and the resulting mixture stirred for 30-60 minutes in a second step of bulk polymerization. Finally, distilled water and a suspending agent are added to disperse the mixture, which is then polymerized with a radical catalyst in a final step of suspension polymerization.

What is claimed is: 
     
       1. A process for preparing an ABS resin having low-gloss properties comprising: a) dissolving between 5 wt % and 20 wt % of a first rubber in a solution of between 30 wt % and 70 wt % of a first aromatic vinyl monomer and between 10 wt % and 50 wt % of a first cyanized vinyl monomer; adding a polymerization controller and radical initiator to form a first reaction mixture; and polymerizing the first reaction mixture at a temperature ranging from about 80° to 120° C. while stirring to achieve an extent of polymerization of between 20 and 50% as first step of bulk polymerization;   (b) adding a second reaction mixture consisting of between 40 wt % and 70 wt % of a second aromatic vinyl monomer, between 10 wt % and 40 wt % of a second cyanized vinyl monomer and between 5 wt % and 15 wt % of a second rubber; and stirring for an additional 30 to 60 minutes as second step of bulk polymerization; and   (c) adding distilled water and a suspending agent to disperse the mixture; and polymerizing with a radical catalyst as step of suspension polymerization.   
     
     
       2. The process as defined in claim 1, wherein said first aromatic vinyl monomer is selected from styrene monomer, α-methyl styrene, p-methyl styrene, vinyl toluene, t-butyl styrene or chlorostyrene. 
     
     
       3. The process as defined in claim 1, wherein said first aromatic vinyl monomer is α-methyl styrene. 
     
     
       4. The process as defined in claim 1, wherein said first cyanized vinyl monomer is selected from acrylonitrile or methacrylonitrile. 
     
     
       5. The process as defined in claim 1, wherein said first rubber is selected from polybutadiene rubber, styrene-butadiene rubber, and EPDM rubber. 
     
     
       6. The process as defined in claim 1, wherein polymerization controller is selected from an aliphatic mercaptan and an aromatic mercaptan. 
     
     
       7. The process as defined in claim 6, wherein said polymerization controller is provided in an amount between 0.001 wt % and 0.3 wt % of the first reaction mixture. 
     
     
       8. The process as defined in claim 1, wherein said radical initiator is a catalyst selected from isopropyl peroxy decarbonate, cumene hydroxy peroxide, benzoyl peroxide, and t-butyl perbenzoate. 
     
     
       9. The process as defined in claim 8, wherein said radical initiator is provided in a amount between 0.005 wt % and 0.5 wt % of the first reaction mixture. 
     
     
       10. The process as defined in claim 1, wherein said second aromatic vinyl monomer is selected from α-methyl styrene and p-methyl styrene. 
     
     
       11. The process as defined in claim 1, wherein said second cyanized vinyl monomer is selected from acrylonitrile or methacrylonitrile. 
     
     
       12. The process as defined in claim 1, wherein said second rubber is polybutadiene rubber. 
     
     
       13. The process as defined in claim 12, wherein said polybutadiene rubber comprises more than 30% cis-form and has a solution viscosity is below 100 centipoise at a concentration of 5% in styrene monomer. 
     
     
       14. The process as defined in claim 1, wherein said suspending agent is tricalcium phosphate. 
     
     
       15. The process as defined in claim 1, wherein said radical catalyst is selected from isopropyl peroxy decarbonate, cumene hydroxy peroxide, benzoyl peroxide, and t-butyl perbenzoate. 
     
     
       16. The process of claim 1 wherein said first step of bulk polymerization forms monomer-occluded spherical rubber particles of which 20-50% are 3-5μ in size, and wherein said second step of bulk polymerization forms lengthwise torn rubber particles of which 10-40% are 1-2μ in size and splinter-shaped rubber particles of which 10-60% are 0.1-0.5μ in size.